Messages in this thread | | | Subject | Re: [Regression 5.6-rc1][Bisected b6231ea2b3c6] Powerpc 8xx doesn't boot anymore | From | Rasmus Villemoes <> | Date | Thu, 13 Feb 2020 08:45:28 +0100 |
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On 12/02/2020 15.24, Christophe Leroy wrote: > Hi Rasmus, > > Kernel 5.6-rc1 silently fails on boot. > > I bisected the problem to commit b6231ea2b3c6 ("soc: fsl: qe: drop > broken lazy call of cpm_muram_init()") > > I get a bad_page_fault() for an access at address 8 in > cpm_muram_alloc_common(), called from cpm_uart_console_setup() via > cpm_uart_allocbuf()
Sorry about that. But I'm afraid I don't see what I could have done differently - the patch series, including b6231ea2b3c6, has been in -next since 20191210, both you and ppc-dev were cc'ed on the entire series (last revision sent November 28). And I've been dogfooding the patches on both arm- and ppc-derived boards ever since (but obviously only for a few cpus).
> Reverting the guilty commit on top of 5.6-rc1 is not trivial. > > In your commit text you explain that cpm_muram_init() is called via > subsys_initcall. But console init is done before that, so it cannot work.
No, but neither did the code I removed seem to work - how does doing spin_lock_init on a held spinlock, and then unlocking it, work? Is everything-spinlock always a no-op in your configuration? And even so, I'd think a GFP_KERNEL allocation under spin_lock_irqsave() would trigger some splat somewhere?
Please note I'm not claiming my patch is not at fault, it clearly is, I just want to try to understand how I could have been wrong about the "nobody can have been relying on it" part.
> Do you have a fix for that ?
Not right now, but I'll have a look. It's true that the patch probably doesn't revert cleanly, but it shouldn't be hard to add back those few lines in the appropriate spot, with a big fat comment that this does something very fishy (at least as a temporary measure if we don't find a proper solution soonish).
Rasmus
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